Investigators are set to examine “conclusively” whether or not the bodies of four men missing since the Dianne trawler sank off Queensland last year are inside the vessel.

Police today began pumping out the water that still fills much of the Dianne’s hull after a long operation to lift the vessel off the seabed and tow it to the Port of Bundaberg finally succeeded.

It is the beginning of the next big step, as authorities prepare for the above-water search.

Six men are believed to have died in the capsizing off the coast of the town of 1770 on October 16, but the remains of just two men - Adam Hoffman, 30, and Ben Leahy, 45 - were found by police divers during searches.

Four other men on board – Eli Tonks, 39; Adam Bidner, 33; Zach Feeney, 28; and Chris Sammut, 34 – are presumed to have died.

Ruben McDornan was the sole survivor of the sinking. He spent 12 hours at sea wearing only a pair of boardshorts, until he was rescued by a passing boat crew.

The search will hopefully provide closure for the victims' families and uncover evidence about the cause of the accident, Queensland Police Service Inspector Pat Swindells said today.

"Once we empty the water out and we get through we'll be able to conclusively say whether or not they're on board," he said of the remains of the four missing men.

"It's most important to give the families some closure, let them continue on the grieving process."

It is estimated the emptying of the Dianne’s hull will take until Thurday, after which events could unfold quickly.

9NEWS understands a chaplain will bless the vessel before a special Disaster Victim Identification Unit steps aboard.

Insp. Swindells said there was a "possibility" the remains of some missing victims may still be on board.

"Police divers did a magnificent job in some very hostile conditions to get in and around the vessel, but this will give… closure," he said.

"It's important we get as much information as we can as to how the Dianne sunk," Insp. Swindells added.

Last Monday, February 12, the Dianne was "partially raised" and salvage crews then prepared it to be lifted to the surface, a police statement said.

On Friday, crews towed the fishing vessel – which was still underwater – to Bundaberg.

"Further inspections" will be conducted on land.

Queensland Premier Annastacia Palaszczuk today said the victims' family and friends "remain in our thoughts and prayers".

"I pay tribute to all those involved the initial search, and those who have worked in the recovery efforts that now allow for thorough investigations into this tragedy," she said in a statement.

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